1. Field of the Invention
The present invention relates to the repair or joining of superalloy components, and more particularly, to the weld built up of nickel base superalloy components, and most particularly, to the welding of nickel base superalloy components containing relatively large amounts of aluminum and/or titanium.
2. Background and Related Art
Superalloys are typically understood to be high-temperature materials which display excellent resistance to mechanical and chemical degradation of properties even as temperatures approach the melting points of the materials. Ni base superalloys are based upon nickel (Ni) and typically contain significant amounts of numerous other elements such as chromium (Cr), aluminum (Al), titanium (Ti), tungsten (W), cobalt (Co), tantalum (Ta), carbon (C), among others. The high-temperature superalloys found early application in aircraft turbine engines. Since a higher operating temperature typically leads to increased fuel efficiency and lower carbon emissions, causing superalloys to find increasing uses in ground-bases turbine systems as well. For example, see The Superalloys, by Roger C. Reed, (Cambridge University Press, 2006, particularly Chapter 1. The entire contents of this reference is incorporated herein by reference for all purposes.
Thus, as superalloys are used in greater numbers of airborne and ground-based turbine systems, and operated at higher temperatures, increasing number of blades vanes and other components are subject to cracking and other forms of material degradation requiring repair. It is important that the repair of such turbine components be effectively carried out to result in repaired components having properties as close as possible to those of the original components.
The economic importance of superalloys has generated considerable research in their welding and repair. See, for example, Welding Metallurgy and Weldability of Nickel-Base Alloys, by J. N. DuPont, J. C. Lippold, Samuel D. Kiser (John Wiley & Sons, 2009), particularly Chapter 4. The entire contents of this reference is incorporated herein by reference for all purposes.
Welding is a commercially important method for repairing or joining Ni base superalloy components. However, as Al and/or Ti are added to the superalloy to improve high temperature strength of the components, it becomes much more difficult to weld the components, typically being subject to cracking or other defects. Thus a need exists in the art for improved methods to weld Ni base superalloy components, particularly those including relatively large amounts of Al and/or Ti.